1. Field of the Invention
The present invention relates to flat cable/flexible circuit to circuit board connectors where the flat cable or flexible circuit itself is the electrical connection media and local thickness variation equalizer and, more particularly, to such connectors specifically adapted for use in electronic devices wearable on the user's wrist, such as electronic watches, calculators and watch-calculator combinations.
2. Description of the Prior Art
There has been required, especially in extremely small electronic devices, such as electronic watches, calculators and the combination thereof, the need to make simple, small, and inexpensive connections. The electrical integrity of the connection must be maintained. Furthermore, these connections must be easily and repeatably connected and disconnected so that the components connected may be replaced and/or repaired in a non-destructive manner. While there has been numerous devices utilized for much larger devices, they have not been entirely successful when applied to miniaturized electronic devices, and are further wasteful of space. Examples of such prior art devices include those described in U.S. Pat. Nos. 2,825,042; 3,082,398; 3,102,767; 3,114,587; 3,158,421; 3,319,216; 3,401,369; 3,461,221; 3,488,620; 3,492,538; 3,533,049; 3,602,870; 3,614,707; 3,629,787; 3,772,775; 3,774,075; and 3,845,236. While all these prior art devices appear to work well or at least satisfactorily for their intended purposes or in their specialized environments, they do not meet the specific requirements described above and embraced by the objects set forth below.
One primary deficiency of the prior art, which is believed to be fairly represented by the above noted patents, is its total disregard of space limitations. Electronic devices, which are intended for wear on a user's wrist or, perhaps, attached by a pin or clasp to one's clothes or hung by a chain from the wearer's neck must, of necessity, be sufficiently small in size not only to be wearable but also to be aesthetically attractive, without detracting from the usefulness or quality of the device. As a consequence, a multitude of components must be crowded into the smallest possible space. While it is possible to permanently electrically couple all the components together by bonding or related methods, repair and replacement of the components became inconvenient, if not impossible, due to the relative ease of destruction by heat or breakage. The prior art relating to electrical connections which may be easily made and disconnected in such a small environment has not recognized, or if recognized, not solved these problems. As a consequence, many prior art connectors utilize a multiplicity of parts, such as exemplified in at least several of the above noted patents.
Also, as a result of the smallness of the connections to be made, it is not possible to use separate spring engaging means, e.g., U.S. Pats. Nos. 2,825,042; 3,082,398; 3,102,767; 3,158,421; 3,461,221; 3,492,538; 3,614,707; and 3,629,787 for the primary reasons that there is insufficient material in the separate tines to maintain proper electrical contact and that the smallness required would result in too great a fragility of the tines. This problem would be less likely to occur if a single length of clamp were utilized; however, then any planar discontinuities may preclude proper pressure between each and every contact-engaging surface. This problem may have been partially the reason for the use of a flexible dielectric sheet in U.S. Pat. 3,401,369, although it must be acknowledged that this patent does not present or discuss this problem. The deficiency of the solution (based upon an assumption that such indeed was an intent in U.S. Pat. No. 3,401,369) is that an additional flexible dielectric sheet bonded to a spring backing is required and entails the use of precious space which is otherwise need either for other components or for lesser device thickness in electronic watches and calculators.
U.S. Pat. No. 3,772,775 is likewise deficient in that, while it is directed to coupling a flat conductor cable to a circuit board, there is no concern as to space requirements in that special enclosures are needed. Furthermore, there is no disclosure whether a single clamping surface of a plurality of tines are used, leading one to believe that there also was no consideration given to the special problems in electronic watches and calculators.